matter cannot be seen and its essence is not known, yet it affects the whole universe by gravity.
The mystery matter covers up to 80 percent of the matter in the universe. Dark matter is needed because visible matter alone does not explain the magnitude of gravity pulling galaxies together.
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Now, an international research team of hundreds of scientists, Des (Dark Energy Survey), mapped dark matter more accurately than ever before.
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Based on three years of measurements, a map was created that describes the distribution of galaxies of visible matter and dark matter in the universe.
“These cosmic-scale structures help us answer the biggest questions in the universe,” said University College London researcher
To New Scientist magazine.
Dark matter cannot be detected directly because it does not reflect light or any other electromagnetic radiation.
Indirect observations can be made with so-called gravity lenses. A gravitational lens is said to be a large object in space that refracts the light emitted by the object behind it.
“All the matter in space, from stars to galaxies, causes the space-time around them to curve, as if placing a heavy ball over a rubber film. By measuring this curvature, it is also possible to detect the effect of dark matter on the space around it, ”says Aalto University physicist
Tenkanen did not participate in Desi’s mapping, but he has studied dark matter.
Scientists are looking for dark matter by observing light coming from distant galaxies. Dark matter bends space-time and makes light meander. The more light goes into a bend, the more often dark matter appears in its path.
In total, there were more than 200 million galaxies under study. The map compiled from them covers up to one-eighth of the Earth’s night sky.
The areas marked clearly on the map are concentrations of dark matter and galaxy clusters that also have our own galaxy.
Black regions represent cosmic voids, that is, regions between galaxy clusters with few or no galaxies. The density of the areas is so low that gravity may behave differently in them.
“Galaxies made of ordinary matter are located on the map where there is even dark matter. Together, they form such a reticulated, soapy foam-like structure, ”says Tenkanen.
The study has not yet been peer reviewed, but most of the papers related to the project are readable In the Arxiv service.
The map illustrates the current structure of the universe, but at the same time tells of the past.
The light from the farthest objects on the map has traveled the Earth for seven billion years. Because the speed of light is finite, by observing these points of light, it is possible to observe how the structures of the universe have evolved over time.
“The deeper we look into space, the farther we can see into the past.”
The researchers used the measurements to test the prevailing standard model of cosmology. It says the universe was born 13.8 billion years ago in an initial explosion, and then expanded
in accordance with general theory of proportionality.
The events following the initial explosion have been most accurately measured by the European Space Agency’s Planck satellite, which was launched into space in 2009.
It formed a map of the initial explosion of the “afterglow,” a cosmic background radiation stretched into microwaves that originated in a universe only 380,000 years old.
Based on these measurements, it has been possible to predict how ordinary and dark matter would have spread from the times of the universe to the present day.
“The researchers investigated whether the prediction based on cosmic background radiation coincides with the current structure of the universe. So it was like comparing the baby portrait of the universe to the images captured from its youth and the present, ”says Tenkanen.
In previous galaxy surveys, some deviations have been observed between the prediction and the current structure. According to the surveys, matter would have been more evenly distributed in the universe than predicted from cosmic background radiation.
Scholars have even wondered if the general theory of relativity could be wrong in some way.
The more comprehensive measurements now published show that such a mismatch is unlikely to exist. The measured differences are so small that they are not statistically significant.
“The results show that there is dark matter in the universe in exactly the same proportions that could have been predicted by measuring cosmic background radiation.”
Source: Tiede by www.tiede.fi.
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